1. Field of the Invention
The present invention relates generally to ammunition and more particularly to hollow point bullets or slugs comprising a cartridge or similar propulsion device.
2. Prior Art
Recent events, particularly the hijacking of airplanes by terrorists and the subsequent loss of life in New York, Pennsylvania and Virginia, have generated a need for new ideas for preventing airplane hijacking. For example, it has been proposed that one or more armed air marshals accompany scheduled airline flights to intervene in the event of an attempted hijacking. Another proposed solution is to arm pilots with weapons capable of selectively and accurately dispensing lethal force against a hijacker. A disadvantage with discharging a conventional weapon on an airplane wherein prior art bullets are the projectile is the danger posed by the bullet passing through the hijacker and striking another person or piercing the fusilage with concomitant loss of air pressure within the plane.
The nose portion of a hollow point bullet expands upon impact with a target media thereby increasing the energy transfer capabilities of the bullet. Typically, this expansion results in a number of petals of metal being formed as the nose portion folds back upon itself, thereby increasing the effective diameter of the bullet. This expansion and resultant petal formation is referred to as xe2x80x9cmushrooming.xe2x80x9d A hollow point bullet may be solid or jacketed. A solid bullet typically comprises a solid piece of metal, such as lead or copper. A jacketed bullet typically comprises a lead core surrounded by a harder metal, such as brass. The jacket is relatively hard and slick, compared to the lead of the core, so the bullet is more resistant to mechanical deformation by the action of the gun as compared to the solid bullet.
Swank, in U.S. Pat. No. 5,943,749, discloses a bullet comprising a slug of generally solid material having an outer surface and an end portion having a cavity therein. A plurality of grooves are formed on the outer surface of the end portion. The end portion of the slug is contoured so that the bullet has a predetermined shape. A plurality of slits may be formed through at least a portion of each of the plurality of grooves. Preferably, the plurality of grooves and slits are formed substantially simultaneously. The slits are formed around a peripheral edge of the end portion of the slug. A plurality of projections, may be formed which extend into the cavity adjacent to the slits. Each of the slits may be formed at an angle with respect to a longitudinal axis of the slug to form each of the projections. The cavity in the end portion has a truncated cone geometry. Hollow Point (HP) projectiles can expand too quickly, resulting in poor penetration, or can only partially expand, leading to over penetration of a target and reduced energy transfer to the target. In addition, hollow point bullets can fail to expand, leading to severe over penetration or pass through.
Benini, in U.S. Pat. No. 6,263,798, discloses a frangible bullet and a method for making it. The frangible bullet is formed from a mixture of metal particles and metal or metalloid binder material which is compacted into the desired shape, heated to a temperature above that needed to form at least one intermetallic compound but below the temperature of joining of the metal particles by sintering and below the temperature of formation of substantial amounts of a ductile alloy of the metal of the particles and the metal or metalloid binder material and then cooled. When such articles are formed into bullets and fired at a target possessed of substantial mass, they have sufficient strength to maintain their integrity during firing but disintegrate into powder on impact. In addition, the bullet may comprise a variety of metals other than lead.
Huffman, in U.S. Pat. No. 6,115,894, discloses an armor-piercing frangible bullet, and provides a historic summary of bullet development as well as a summary of test data obtained for commercially available small arms ammunition. In particular applications it may be desirable to provide a hollow point, frangible bullet that can be subjected to ballistic inspection following impact with a target. Ballistic testing of a bullet requires that a substantial portion adjacent the base of a bullet (i.e., a shank) remain intact when presented for testing. Thus, it is desirable to provide a bullet that may be designed to possess attributes of both hollow point and frangible bullets and which, upon impact with a target, retains a recoverable shank of predetermined size that is suitable for ballistic characterization and identification.
Most ammunition projectiles, particularly the newer non-lead frangible projectiles, perform poorly in the sub-sonic range. Many ammunition manufacturers use high velocities to enhance the frangibility (break up) of the bullet upon impact. Prior art frangible projectiles can fail to fragment if the chemical process used to make the bullet is not carefully controlled. In addition, such frangible bullets operate best when fired at very high velocities, and are loaded by ammunition manufacturers at high pressures. Further, the fragmentation pattern is random and generally forms asymmetric clusters with respect to the direction of the primary wound channel.
While both frangible bullets and mushrooming hollow point bullets are known in the art, and wherein each has unique attributes that recommend it for specific situations, there continues to be a present and urgent need for improved bullets that can be fired by conventional weapons such as pistols and will minimize the danger of collateral damage in the event of a hijacking or similar situation wherein shoot-through injuries to innocent non-target people is probable.
It is a primary object of the present invention to provide a frangible hollow point bullet adapted to be used in conventional small arms cartridges.
It is another object of the invention to provide a bullet meeting the primary objective, set forth above, wherein a shank portion of the bullet that is suitable for ballistic analysis is recoverable after impact of the bullet with a target.
It is a further object of the invention to provide a frangible hollow point bullet that fragments on impact with a target and wherein the size of the fragments is substantially controllable and uniform.
It is yet a further object of the invention to provide a frangible bullet that fragments upon impact with a target and wherein the spatial distribution of bullet fragments is substantially symmetric through a solid angle centered on the trajectory of the bullet prior to impact with the target.
The above objectives of the invention are met by a substantially bullet-shaped projectile having a leading end, a trailing end and a frangible body portion therebetween. The projectile has a hollow cavity opening onto the leading end of the body portion and extending rearwardly therefrom into the body portion. The hollow cavity comprises a plurality of coaxial cylindrical cavities, wherein the diameter of each rearwardly adjacent cylindrical cavity comprising the hollow cavity decreases stepwise, in discrete increments, in a direction rearward of said leading end. In a preferred embodiment of the projectile, at least one of the cylindrical cavities has a cavity wall bearing stress risers thereon. In a most preferred embodiment of the projectile, all of the cylindrical cavities comprising the hollow cavity have a pattern of stress risers on the wall thereof. Examples of suitable patterns of stress risers include a diamond-shaped pattern of grooves, a plurality of parallel grooves, a plurality of horizontal and or vertical grooves and so forth. The depth of the hollow cavity relative to the axial length of the projectile can be varied to control the fragmentation pattern and the size of the intact, recoverable base or shank. The inclusion if stress risers within the hollow cavity provides means for controlling fragment size upon impact. Preferred projectiles include bullets and shotgun slugs. In an embodiment of a shotgun slug having a hollow cavity in the rearward trailing end thereof, the wall of the hollow cavity includes stress risers thereon. The outer lateral surface of the projectile is preferably smooth. The leading end of the hollow cavity may be conically flared.